let form = new Form(Text = "F# Windows Form",
                    Visible = true,
                    TopMost = true)
form.MouseClick
    |> Event.merge(form.MouseDoubleClick)
    |> Event.add ( fun evArgs ->
        form.BackColor <- System.Drawing.Color.FromArgb(
            evArgs.X, evArgs.Y, evArgs.X ^^^ evArgs.Y) )